Lectins are a class of proteins which bind to carbohydrates. Because of their specificity in binding, they will distinguish between various carbohydrate configurations. They are used extensively as probes of cell surface architecture. Many of the lectins are being used to detect the cancerous state, as several will preferentially agglutinate transformed cells. When lectins bind to cells, several physiological functions can be altered. For example, several will induce mitogenesis in lymphocytes. The single most studied lectin is concanavalin A from jack bean. It binds carbohydrates such as glucose and mannose units and will agglutinate a variety of cells by acting as a cross-link between cell surfaces. The protein itself requires two metal ions for activity. A second lectin with different sugar-binding specificity can be isolated from lima bean. This lectin is blood type A specific and has also been shown to be capable of altering the physiology of cells to which it binds. Like cancanavalin A, it requires metal ions for carbohydrate binding activity. A thorough understanding of the carbohydrate binding mechanisms will be necessary in order to describe the ways in which lectins influence cells. Although lectins are already widely used, a characterization of their action will enhance their usefulness in studying cell surfaces and the transformed state. Nuclear magnetic resonance (NMR) spectroscopy and electron spin resonance (ESR) spectroscopy will be used to study the metal ion function in activating the two lectins. Kinetics of metal ion association will be used to examine conformational changes and cooperativity between subunits. NMR spectra of the protein itself will be used to study metal ion-induced changes in protein structure. The relationship of the bound carbohydrate to the metal ions will be determined by distance measurements from NMR studies.